J ournal o/Glacio{olfY, Vol. 18, No. 79,1977 GLACIOLOGICAL PROBLEMS SET BY THE CONTROL OF DANGEROUS LAKES IN CORDILLERA BLANCA, PERU. I. HISTORICAL FAILURES OF MORAINIC DAMS, THEIR CAUSES AND PREVENTION By LOUIS LLIBOUTRY, (Laboratoire de Glaciologie du CNRS, Grenoble, France) BENJAMiN MORALES ARNAO, (Instituto de Geologia y Mineria, Lima, Peru) ANDRE P AUTRE, (G eoconseil, La Celle-St-Cloud, France) and BERNARD SCHNEIDER (Coyne et Bellier, Paris, France) ABSTRACT. The retreat of glaciers since 1927 in Cordillera Blanca has produced dangerous lakes a t the front of many glaciers. All the known data, most of them unpublished , are reviewed. The known aluviones are listed, and those of Chavin, Quebrada Los Cedros and Artesoncocha described in full. In these three cases a breach in the front mo ra ine came from big ice falls into the lake. The protective d evices made on the outlets are described, as well as the effects of the big earthquake on 3 I M ay 1970. In the case of Laguna Paran, which keeps its level thanks to infiltrations, the fluctuations of the discharge of the springs as related to the level of the lake from 1955 to 1969 are reported. The projects for lowering the level of Laguna Paran and for emptying Safuna Alta a re described. The latter partially emptied in fact by piping a fter the earth­ quake, allowing a final solution. REsu ME. Problemes glaciologiques souleves par le cOlltrole de lacs dallgereux dalls la Cordillera Blanca, Perou. f. Ruptures historiques de barrages morailliques, leur causes et leur prevelltioll. L e retrait des glaciers d epuis 1927 dans la Cordillera Blanca a cree des lacs dangereux au fro nt de nombreux glaciers. On passe en revue tous les documents disponibles, la plupart non publies. La liste des aluviolles connus est etablie, et ceux de Chavin, de la Quebrada Los Cedros et d ' Artesoncocha comple tement decrits. Da ns les trois cas la breche dans la moraine frontale fut la consequence de grosses chutes de glace dans le lac. On decrit les ouvrages de pro­ tection faits sur les exutoires, ainsi que les effets du tremblement de terre du 31 Mai 1970. Dans le cas de la Laguna Paran, qui maintient son niveau grace a d es infiltrations, on donne les variations du debit des sources en fonction du niveau du lac entre 1955 et 1969. On decrit les projets pour baisser le niveau de la Laguna Paran et pour vider Safuna Alta. Cette derniere se vida a moitie en fait apres le seisme par forma tion de renards, permettant une solution definitive. ZUSAMM EN FASSUNG. Glaziologische Probleme bei der VberwachulIg gifiihrlicher Seell ill der Cordillera Biallca VO Il Peru. f. Historisch, Briiche VO Il Moriillelldiimmen, ill re Ursachen , iilre Verhiitullg. Der Gletscherruckgang in der Cordillera Bla nca seit 1927 hat zur Bildung gefa hrlicher Seen vor d er Zunge vieler Gletscher gefuhrt. Alle bekannten Daten, die meist noch unveroffentlicht si nd, werden hera ngezogen. Die beka nnten Ausbriiche (aluuiolles ) werden aufgefiihrt, j ene von Chavin, Quebrada Los Cedros und der Artesoncocha ausfiihrlich beschrieben. In den drei Fallen fuhrten gewaltige Eislawinen in den See zu Briichen in der Damm-Mora ne. Die Schutzmass nahmen a n d en Ausflussen werden beschrieben, ebenso die Auswirkungen des grossen Erdbebens vom 3!.. Mai 1970. Fur den Laguna Paran, der sein Niveau infolge von Infiltrationen halten kann, werden die Anderungen d er Quellschiittung im Vergleich zur H ohe d es Seespiegels zwischen 1955 und 1969 zusammengestellt. Die Pla ne zur Absenkung des Laguna Pa ran und zur Leerung der Safuna Alta werden beschrieben. Die letzte re leerte sich in der Tat zur Halfte nach dem Erdbeben durch R ohrleitungs­ bildung und e rlaubte eine endgultige Losung. HISTORICAL In this article and the two companion papers, field data collected in Cordillera Blanca, Peru, during the years 1967 to 1970 are reported. Since then they have been lying in drawers as unpublished and even restricted reports (Coyne et Bellier, Geoconseil, unpublished [aJ to re]; Lliboutry and others, unpublished). In order to lower the water level in two dangerous lakes, Paron and Safuna Alta, the hydroelectric power agency of the Rio Santa basin known as Corporacion Peruana del Santa, 239 Downloaded from https://www.cambridge.org/core. 02 Oct 2021 at 05:03:36, subject to the Cambridge Core terms of use. JO U RNAL OF GLACIOLOGY CPS (now united with other power agencies of Peru to form Electroperu), hired in 1967 as con­ sultants two engineering offices, Coyne et Bellier and Geoconseil , from Paris. Paron was visited in February 1967 by Lliboutry, Morales, Pautre and Post; Safuna in July 1967 by Lliboutry, Morales and Pautre. From July 1967 to May 1969, B. Schneider remained in the Call ejon de Huaylas to supervise the workings (Callejon de Huaylas is the valley of upper Santa river, between Cordillera Blanca and Cordillera Negra). In May 1969, the late J. Grador, with Lliboutry and Pautre, came back to P eru to study several lakes which may be used for hydroelectricity around Nevado Santa Cruz. This time they had at their disposal an Alouette Ill, the only helicopter able to fl y at an altitude over 6000 m . Then the big castastrophe of 3 1 May 1970 took place. Yungay and its 15 000 inhabitan ts disappeared under the mud, 90% of the buildings of Huaraz were des troyed by the earth­ quake, 70% of Caraz and Carhuas. B. Morales and other engineers of CPS who were living in the Callejon were lucky to survive. On 9 and 10 June IV[orales was able to fly in a helicopter over the main dangerous lakes, together with Lliboutry (who had been sent by UNESCO, on request of the Peruvian government). Also at the request of Peru, UNESCO and PNUD sent a commission to study possible sites for new cities. It was formed by B. Schneider, Professor V. Mencl from Brno and Dr M . Vallon from Grenoble. They remained in the area from August to O ctober 1970, and among other surveys examined the dangerous lakes above Carhuas and Huaraz. CARTOGRAPHY AND AERIAL COVERAGES Until recently the only detailed map of the area w ere the two sheets at the scale of I : 100000 drawn from terrestrial photogrammetry in 1932 and 1939 and known as Kinz]'s map. During the Cordillera-Blanca Expedition des D eutschen und Osterreichischen Alpenvereins 1932 (under the leadership of Dr Borchers), E. H ein, B. Lukas and H . Kinzl surveyed the northern part of Cordillera Blanca and Callejon de Huaylas between Nevado Champara and Huaraz. The corresponding sheet was published in 1935 in Die W eisse Kordillere (Borchers, editor). Explanations are given in Kinzl (1942). The bottom of many quebradas, specially the region of the Safuna lakes could not be plotted. During the Anden-KundJahrt des Deutschen Alpenvereins in 1939- 40, K. H eckler and H. Kinzl surveyed the southern part. The sheet was printed in 1945 and included in the first issue of the Zeitschrift Jilr Gletscherkunde und Glazialgeologie (1949). I t was published again with explana­ tions in Kinzl (1964). M eanwhile aerial coverages of the Cordillera had b een made. The United States Air Force (USAF) took trimetrogon pictures in 1943 and a single line of vertical photographs in [948 (project No. 3093). In 1948- 50 the Servicio Aerofotografico Nacional (SAN) of the Peruvian Air Force covered the Cordillera Blanca, using a camera of 23 cm X 23 cm, with a focal length of 6 inches (0.152 4 m) (project No. 2524). The altitude of flight was 27 000 ft (8230 m). With these pictures an orthophotoplan at scale 1 : 20000, and then a reduction at 1 : 142 000 were made, on sale at SAN. Under contract AST 9 of the Instituto Geogn1fico Militar del Peru (IGM), the USAF made a coverage of a great part of Peru in 1962- 63, using the same type of camera, and with a flight altitude of 30 000 ft (9 144 m). It is now being plotted, simultaneously by IGM and by the Servicio Cartografico del Ministerio de Agricultura para Reforma Agraria y Catastro, in order to draw maps at 1 : 25000, but priority has been given to areas which do not include Cordillera Blanca. Under contract from Corporacion Peruana del Santa, the SAN made its own coverage of Cordillera Blanca in 1966- 68 (Project No. 147-66-A), again with a focal length of 6 inch es, (0.1524 m ), and with 26000 ft (7 925 m ) as altitude offlight, and plotted it at scale 1 : 25000. Downloaded from https://www.cambridge.org/core. 02 Oct 2021 at 05:03:36, subject to the Cambridge Core terms of use. GLACIOLOGICAL PROBLEM S OF PERUVIAN LAKE S. I It is an invaluable document, but with very p oor dmwing of the limits of glaciers, and available only as ozalid copies. Thus for Safuna for instance we had at our disposal vertical stereoscopic pairs taken in 1950, 1963, 1966 and 1968. When the land is at an altitude of 4420 m and the flights were made at 30000 ft (9 145 m), 27000 ft (8230 m ) and 26000 ft (7925 m), the scale of the con tact pictures is respective! y 1 : 31 000, 1 : 25 000 and 1 : 23 000. After the disaster, the Callej6n de Huaylas and the wes tern slopes of the Cordillera Blanca were covered by SAN (Proj ect 176-70-A) and NASA ( 13- 18 July 1970, at 28000 ft (8535 m)) . FORMATION OF LAKES O N GLACIAL TONGUES With the exception of Huasca dm Norte (6655 m), which had been climbed in 1908 by Miss Peck with two guides from Zermatt (R.